Battery

Abstract

Provided is a battery that has higher reliability. This battery comprises a battery element that includes a first electrode and a second electrode, an outer case member that accommodates the battery element, an outer terminal that is attached to the outer case member with an insulating member interposed therebetween, a first electrode lead that connects the first electrode and an inner surface of the outer terminal, and a second electrode lead that connects the second electrode and an inner surface of the outer case member. At least one of the first electrode lead and the second electrode lead has a first end portion, a central portion, and a second end portion in the stated order along a width direction that is orthogonal to the longitudinal direction of the electrode lead, the central portion being flat in shape and being welded to the inner surface of the outer terminal or the inner surface of the outer case member. At least one of the first end portion and the second end portion is folded in a direction away from the inner surface of the outer terminal or the inner surface of the outer case member.

Description

[Technical Field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small, lightweight, and capable of achieving high energy density. These secondary batteries include a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been conducted on the configuration of these secondary batteries (see, for example, Patent Document 1).

[0003] For example, Patent Document 1 describes a sealed electricity storage device that includes an electrode body in which a positive electrode body and a negative electrode body are stacked or wound with a separator interposed therebetween, and an exterior case that houses the electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-46639 Summary of the Invention

[0005] Various studies have been conducted to improve the performance of secondary batteries, but there is still room for improvement in the performance of secondary batteries.

[0006] Therefore, it is desirable to provide a battery with higher reliability.

[0007] A battery according to an embodiment of the present disclosure includes a battery element including a first electrode and a second electrode, a housing member housing the battery element, an external terminal attached to the housing member via an insulating member, a first electrode lead connecting the first electrode to the inner surface of the external terminal, and a second electrode lead connecting the second electrode to the inner surface of the housing member. At least one of the first electrode lead and the second electrode lead has a first end, a central portion, and a second end, in that order, along a width direction perpendicular to its longitudinal direction, and the central portion is flat and welded to the inner surface of the external terminal or the inner surface of the housing member. At least one of the first end and the second end is bent in a direction away from the inner surface of the external terminal or the inner surface of the housing member.

[0008] According to the battery of the embodiment of the present disclosure, at least one of the first end and the second end of at least one of the first electrode lead and the second electrode lead is bent in a direction away from the inner surface of the external terminal or the inner surface of the exterior member, thereby providing higher reliability.

[0009] Note that the effects of the present disclosure are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view illustrating the configuration of a secondary battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view illustrating the configuration of the secondary battery shown in FIG. [Figure 3] FIG. 3 is a partial cross-sectional view showing the configuration of the battery element shown in FIG. [Figure 4A] FIG. 4A is a plan view illustrating the configuration of the positive electrode lead shown in FIG. [Figure 4B] FIG. 4B is a first cross-sectional view illustrating the configuration of the positive electrode lead shown in FIG. [Figure 4C] FIG. 4C is a second cross-sectional view illustrating the configuration of the positive electrode lead shown in FIG. [Figure 5A]FIG. 5A is a plan view illustrating the configuration of the negative electrode lead shown in FIG. [Figure 5B] FIG. 5B is a first cross-sectional view illustrating the configuration of the negative electrode lead shown in FIG. [Figure 5C] FIG. 5C is a second cross-sectional view illustrating the configuration of the negative electrode lead shown in FIG. [Figure 6] FIG. 6 is a perspective view showing the structure of an outer can used in the manufacturing process of the secondary battery shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order. 1. Secondary battery of one embodiment 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Action and effects

[0012] <1. Secondary battery> First, a secondary battery according to an embodiment of the present disclosure will be described.

[0013] The secondary battery described here has a flat, columnar, three-dimensional shape and is referred to as a coin type or button type. As will be described later, this secondary battery has a pair of opposing bottoms and a sidewall portion located between the pair of bottoms. In this secondary battery, the height is smaller than the outer diameter. The "outer diameter" here refers to the maximum diameter (maximum outer diameter) of the bottoms. In this secondary battery, the maximum diameters of the pair of opposing bottoms are substantially equal to each other. Furthermore, the "height" here refers to the maximum distance from the upper surface of one bottom to the lower surface of the other bottom. In this embodiment, the direction in which the pair of bottoms face each other is defined as the height direction Z.

[0014] The charge / discharge principle of a secondary battery is not particularly limited, but the following description will be given of a case in which battery capacity is obtained by utilizing the absorption and desorption of an electrode reactant. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode to prevent deposition of the electrode reactant on the surface of the negative electrode during charging. That is, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode. The secondary battery of this embodiment is a high-charge voltage secondary battery that can exhibit good cycle characteristics without reducing energy density even when charged at a high voltage of 4.38 V or higher.

[0015] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0017] <1-1.Configuration> Fig. 1 shows a perspective view of a secondary battery. Fig. 2 shows a cross-sectional view of the secondary battery shown in Fig. 1. Fig. 3 shows a cross-sectional view of a battery element 40 shown in Fig. 2. However, Fig. 3 shows an enlarged view of only a portion of the cross-sectional view of the battery element 40.

[0018] In the following description, for convenience, the upper side in each of FIGS. 1 and 2 will be referred to as the upper side of the secondary battery, and the lower side in each of FIGS. 1 and 2 will be referred to as the lower side of the secondary battery.

[0019] As shown in FIG. 1, the secondary battery described here has a three-dimensional shape in which the height H is smaller than the outer diameter D, i.e., a flat and columnar three-dimensional shape. Here, the three-dimensional shape of the secondary battery is flat and cylindrical (columnar). In this embodiment, the vertical direction of the paper in each of FIGS. 1 and 2 is defined as the height direction Z. Therefore, the height H means the dimension of the secondary battery of this embodiment in the height direction Z. Furthermore, the outer diameter D means the dimension of the secondary battery of this embodiment in the direction perpendicular to the height direction Z.

[0020] The dimensions of the secondary battery are not particularly limited, but as an example, the outer diameter D is 3 mm to 30 mm and the height H is 0.5 mm to 70 mm. However, the ratio of the outer diameter D to the height H (D / H) is greater than 1. In other words, the outer diameter D is greater than the height H. The upper limit of this ratio (D / H) is not particularly limited, but is preferably 25 or less.

[0021] 1 to 3, this secondary battery includes an outer can 10, an external terminal 20, a battery element 40, and a positive electrode lead 51. Here, the secondary battery further includes a gasket 30, a negative electrode lead 52, a sealant 61, and insulating films 62 and 63.

[0022] [Outer can] 1 and 2, the exterior can 10 is a hollow exterior member that houses the battery element 40 etc. The exterior can 10 is made of a conductive material.

[0023] Here, the exterior can 10 has a flat, approximately cylindrical three-dimensional shape corresponding to the three-dimensional shape of the secondary battery, which is flat and cylindrical. Therefore, the exterior can 10 has a pair of bottoms M1, M2 facing each other and a side wall M3 located between the bottoms M1, M2. That is, the side wall M3 connects the bottoms M1 and M2 and surrounds the battery element 40. The upper end of the side wall M3 is connected to the bottom M1. The lower end of the side wall M3 is connected to the bottom M2. As described above, the exterior can 10 has an approximately cylindrical shape. The planar shapes of the bottoms M1, M2 are each circular, and the surface of the side wall M3 is a convex curved surface.

[0024] The outer can 10 also includes a storage section 11 and a lid section 12 that are welded to each other. That is, the internal space of the outer can 10 is sealed by welding the lid section 12 to the storage section 11. In this embodiment, the bottom section M1 forms the lid section 12, and the bottom section M2 and the side wall section M3 form the storage section 11 together. Therefore, the outer edge of the lid section 12 is welded to the upper end of the side wall section M3.

[0025] The storage section 11 is a flat, cylindrical storage member that stores the battery element 40 and the like inside. The storage section 11 has a hollow structure with an open upper end and a closed lower end. That is, the storage section 11 has an opening 11K (FIG. 2) at the upper end as an insertion port through which the battery element 40 can be inserted in the height direction Z.

[0026] The lid 12 is a substantially disk-shaped lid member that closes the opening 11K of the storage section 11 and has a through hole 12K. The through hole 12K is used as a connection path for connecting the battery element 40 and the external terminal 20 to each other. As described above, the lid 12 is welded to the storage section 11 at the opening 11K. The external terminal 20 is attached to the lid 12 via a gasket 30. That is, the lid 12 supports the external terminal 20 via the gasket 30. The external terminal 20 is attached to the lid 12 via the gasket 30 so as to overlap with and close the through hole 12K. The external terminal 20 is electrically insulated from the outer can 10.

[0027] As described above, in the completed secondary battery, lid portion 12 is welded to storage portion 11. As described above, opening portion 11K is closed by lid portion 12. Therefore, even if one looks at the exterior of the secondary battery, it may not be possible to determine whether storage portion 11 had opening portion 11K.

[0028] However, if the lid 12 is welded to the storage section 11, weld marks remain on the surface of the outer can 10, more specifically, on the boundary between the storage section 11 and the lid 12. Based on the presence or absence of the weld marks, it can be confirmed after the fact whether or not the storage section 11 had the opening 11K.

[0029] That is, if there are weld marks remaining on the surface of the outer can 10, it means that the storage section 11 had an opening 11K. On the other hand, if there are no weld marks remaining on the surface of the outer can 10, it means that the storage section 11 did not have an opening 11K.

[0030] The lid portion 12 is bent so as to partially protrude along the height direction Z toward the inside of the storage portion 11, forming a recessed portion 12H. That is, when viewed from the outside of the outer can 10, the lid portion 12 has a shape that is partially recessed in the height direction Z toward the battery element 40 housed inside the outer can 10. The recessed portion 12H includes a through-hole 12K that penetrates in the height direction Z, a bottom portion 12HB that surrounds the through-hole 12K along a horizontal plane perpendicular to the height direction Z, and a wall portion 12HW that stands along the outer edge of the bottom portion 12HB.

[0031] The portion of the lid 12 other than the recessed portion 12H is a peripheral portion 12R. The peripheral portion 12R is annular and surrounds the recessed portion 12H in a horizontal plane perpendicular to the height direction Z of the secondary battery. The peripheral portion 12R surrounds the periphery of the recessed portion 12H and protrudes in the height direction Z away from the battery element 40. Therefore, in the height direction Z, the surface 12HS of the bottom portion 12HB of the recessed portion 12H is located lower toward the interior of the storage portion 11 than the surface 12RS of the peripheral portion 12R. That is, in the height direction Z, the distance between the surface 12HS of the bottom portion 12HB of the recessed portion 12H and the battery element 40 is shorter than the distance between the surface 12RS of the peripheral portion 12R and the battery element 40.

[0032] The planar shape of the recessed portion 12H, i.e., the shape defined by the outer edge of the recessed portion 12H when the secondary battery is viewed from above, is not particularly limited. Here, the planar shape of the recessed portion 12H is approximately circular. The inner diameter and depth of the recessed portion 12H are not particularly limited and can be set arbitrarily. However, the depth of the recessed portion 12H is set so that when the external terminal 20 is attached to the recessed portion 12H via the gasket 30, the height position of the surface 20S of the external terminal 20 is lower than the height position of the surface 12RS of the peripheral portion 12R.

[0033] As described above, the outer can 10 is a so-called welded can, in which the storage section 11 and the lid section 12, which were previously physically separate from each other, are welded together. As a result, the outer can 10 after welding is a single, physically integrated member, and therefore cannot be separated into the storage section 11 and the lid section 12 later.

[0034] The exterior can 10, which is a welded can, is different from a crimp can formed using a caulking process and is a so-called crimpless can. This is because the element space volume increases inside the exterior can 10, thereby increasing the energy density per unit volume. This "element space volume" refers to the volume (effective volume) of the internal space of the exterior can 10 that can be used to store the battery element 40.

[0035] Furthermore, the exterior can 10, which is a welded can, does not have any overlapping portions, nor does it have any portion where two or more members overlap each other.

[0036] "Having no overlapping parts" means that the outer can 10 is not processed (folded) so that parts thereof are overlapping each other. Also, "having no overlapping parts of two or more components" means that the outer can 10 is physically a single component after the secondary battery is completed, and therefore the outer can 10 cannot be separated into two or more components afterward. In other words, the state of the outer can 10 in the completed secondary battery is not a state in which two or more components are combined while overlapping each other so that they can be separated afterward.

[0037] Here, the outer can 10 is conductive. More specifically, the storage portion 11 and the lid portion 12 are both conductive. The outer can 10 is electrically connected to the negative electrode 42 of the battery element 40 via the negative electrode lead 52. Therefore, the outer can 10 also serves as an external connection terminal for the negative electrode 42. The secondary battery of this embodiment does not need to include an external connection terminal for the negative electrode 42 separate from the outer can 10, and therefore a reduction in the element spatial volume due to the presence of the external connection terminal for the negative electrode 42 is suppressed. This increases the element spatial volume, thereby increasing the energy density per unit volume.

[0038] Specifically, the exterior can 10 is a metal can containing one or more conductive materials such as metal materials and alloy materials. The conductive materials constituting the metal can include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316. However, the materials forming the storage section 11 and the lid section 12 may be the same or different.

[0039] The lid 12 is insulated via a gasket 30 from an external terminal 20 serving as a terminal for external connection of the positive electrode 41. This is to prevent contact, i.e., a short circuit, between the outer can 10 serving as a terminal for external connection of the negative electrode 42 and the external terminal 20 serving as a terminal for external connection of the positive electrode 41.

[0040] [External terminal] 1 and 2, the external terminal 20 is a connection terminal that is connected to an electronic device when the secondary battery is mounted in the electronic device. As described above, the external terminal 20 is attached to and supported by the lid portion 12 of the outer can 10. The external terminal 20 is provided on the opposite side of the lid portion 12 from the bottom portion M2, at a position that overlaps with the through-hole 12K in the height direction Z.

[0041] Here, the external terminal 20 is connected to the positive electrode 41 of the battery element 40 via the positive electrode lead 51. Therefore, the external terminal 20 functions as an external connection terminal for the positive electrode 41. As a result, when the secondary battery is in use, the secondary battery is connected to an electronic device via the external terminal 20 (external connection terminal for the positive electrode 41) and the outer casing 10 (external connection terminal for the negative electrode 42). Therefore, the electronic device can operate using the secondary battery as a power source.

[0042] The external terminal 20 is a flat, approximately plate-shaped member extending along a horizontal plane perpendicular to the height direction Z of the secondary battery. It is disposed within the recessed portion 12H via the gasket 30. The external terminal 20 is insulated from the lid portion 12 via the gasket 30. As shown in FIG. 2 , the surface 20FS of the external terminal 20 in the height direction Z is lower toward the battery element 40 than the surface 12RS of the peripheral portion 12R of the outer can 10. That is, the external terminal 20 is housed within the recessed portion 12H so that its upper end, the surface 20FS, is recessed toward the battery element 40 relative to the surface 12RS. In the secondary battery of this embodiment, the height of the secondary battery is reduced compared to when the external terminal 20 protrudes above the lid portion 12. This increases the energy density per unit volume of the secondary battery. Furthermore, it is possible to prevent short-circuiting between the outer can 10 and the external terminal 20 via other conductive members. In this embodiment, the peripheral portion of the external terminal 20 overlaps with the bottom portion 12HB of the recessed portion 12H in the height direction Z. Having an overlapping portion between the external terminal 20 and the lid portion 12 can improve the mechanical strength of the secondary battery as a whole. Here, the length of the overlapping portion between the external terminal 20 and the peripheral portion along a horizontal plane perpendicular to the height direction Z is preferably greater than the thickness of the external terminal 20 and the thickness of the bottom portion 12HB.

[0043] The outer diameter of the external terminal 20 is smaller than the inner diameter of the recessed portion 12H. Therefore, the outer edge 20T of the external terminal 20 is spaced apart from the lid portion 12. The gasket 30 is disposed only in a portion of the area between the external terminal 20 and the lid portion 12 (recessed portion 12H). More specifically, the gasket 30 is disposed only in a location where the external terminal 20 and the lid portion 12 would come into contact with each other if the gasket 30 were not present. However, it is preferable that the gasket 30 is also disposed between the inner wall surface of the wall portion 12HW of the recessed portion 12H and the outer edge 20T of the external terminal 20. It is also preferable that the lid portion 12 and the external terminal 20 are fixed together by the gasket 30.

[0044] The external terminal 20 includes one or more conductive materials such as metal materials and alloy materials, and the conductive materials include aluminum and aluminum alloys. However, the external terminal 20 may be formed from a clad material. This clad material includes an aluminum layer and a nickel layer, in that order from the side closest to the gasket 30, and the aluminum layer and the nickel layer are roll-bonded to each other in the clad material.

[0045] [gasket] As shown in Fig. 2, the gasket 30 is an insulating member disposed between the outer can 10 (lid portion 12) and the external terminal 20. The external terminal 20 is fixed to the lid portion 12 via the gasket 30. The gasket 30 has a ring-like planar shape with a through hole at a position corresponding to the through hole 12K. The gasket 30 contains one or more types of insulating materials such as insulating polymer compounds, and the insulating materials are resins such as polypropylene and polyethylene.

[0046] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is disposed in the gap between the upper surface of the lid 12 and the lower surface of the external terminal 20 inside the recess 12H. However, as described above, it is preferable that the gasket 30 is also provided between the inner wall surface of the wall 12HW of the recess 12H and the outer edge 20T of the external terminal 20. It is also preferable that the lid 12 and the external terminal 20 are fixed together by the gasket 30.

[0047] [Battery element] 2 and 3, the battery element 40 is a power generating element that causes charge / discharge reactions to proceed, and is housed inside the outer can 10. The battery element 40 includes a positive electrode 41 and a negative electrode 42. Here, the battery element 40 further includes a separator 43 and an electrolytic solution (not shown) that is a liquid electrolyte.

[0048] 2 is a line segment corresponding to the center of the battery element 40 in the direction along the outer diameter D of the secondary battery (external can 10). In other words, the position P0 of the center line PC corresponds to the position of the center of the battery element 40.

[0049] The battery element 40 is a so-called wound electrode body. That is, in the battery element 40, a positive electrode 41 and a negative electrode 42 are stacked one on top of the other with a separator 43 interposed therebetween. Furthermore, as shown in FIG. 2, the stacked positive electrode 41, negative electrode 42, and separator 43 are wound around a center line PC as a winding axis. The positive electrode 41 and the negative electrode 42 are wound while maintaining a state in which they face each other with the separator 43 interposed therebetween. Therefore, a winding central space 40K is formed at the center of the battery element 40.

[0050] Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound such that the separator 43 is disposed at the outermost and innermost peripheries of the wound electrode body. The number of windings of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily. At the outermost periphery of the battery element 40, the negative electrode 42 is disposed outside the positive electrode 41. That is, the outermost positive electrode portion of the positive electrode 41 included in the battery element 40, which is located at the outermost periphery, is disposed inside the outermost negative electrode portion of the negative electrode 42 included in the battery element 40. Here, the outermost positive electrode portion refers to the outermost portion of the positive electrode 41 in the battery element 40, which corresponds to one circumference. The outermost negative electrode portion refers to the outermost portion of the negative electrode 42 in the battery element 40, which corresponds to one circumference. Meanwhile, at the innermost periphery of the battery element 40, the negative electrode 42 may be disposed inside the positive electrode 41. That is, the negative electrode innermost circumferential portion, which is located at the innermost periphery of the negative electrode 42 included in the battery element 40, may be located more inside than the positive electrode innermost circumferential portion, which is located at the innermost periphery of the positive electrode 41 included in the battery element 40. Here, the positive electrode innermost circumferential portion refers to the innermost part of the positive electrode 41 in the battery element 40, which corresponds to one circumference. The negative electrode innermost circumferential portion refers to the innermost part of the negative electrode 42 in the battery element 40, which corresponds to one circumference.

[0051] The battery element 40 has a three-dimensional shape similar to that of the outer can 10. Specifically, the battery element 40 has a flat, approximately cylindrical three-dimensional shape. Compared to a case in which the battery element 40 has a three-dimensional shape different from that of the outer can 10, when the battery element 40 is housed inside the outer can 10, so-called dead space, specifically, a gap between the outer can 10 and the battery element 40, is less likely to occur. This allows the internal space of the outer can 10 to be used effectively. As a result, the element space volume increases, and the energy density per unit volume of the secondary battery increases.

[0052] (positive electrode) The positive electrode 41 is a first electrode used to promote charge / discharge reactions, and as shown in FIG. 3, includes a positive electrode current collector 41A and a positive electrode active material layer 41B.

[0053] Positive electrode current collector 41A has a pair of surfaces on which positive electrode active material layers 41B are provided. Positive electrode current collector 41A contains a conductive material such as a metal material, and the metal material is aluminum or the like.

[0054] The positive electrode active material layer 41B is provided on both sides of the positive electrode current collector 41A and contains one or more types of positive electrode active materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 41B may be provided on only one side of the positive electrode current collector 41A. The positive electrode active material layer 41B may further contain a positive electrode binder, a positive electrode conductive agent, and the like. The method for forming the positive electrode active material layer 41B is not particularly limited, but specifically includes a coating method, etc.

[0055] The positive electrode active material contains a lithium compound. This lithium compound is a general term for compounds containing lithium as a constituent element, and more specifically, compounds containing lithium and one or more transition metal elements as constituent elements. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more other elements (excluding lithium and transition metal elements). The type of lithium compound is not particularly limited, but specific examples include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO2, LiCoO2, and LiMn2O4, and specific examples of phosphate compounds include LiFePO4 and LiMnPO4.

[0056] The positive electrode binder contains one or more of synthetic rubber and polymer compounds. The synthetic rubber is styrene-butadiene rubber, and the polymer compound is polyvinylidene fluoride. The positive electrode conductor contains one or more of conductive materials such as carbon materials, and the carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the conductive material may also be a metal material or a polymer compound.

[0057] (Negative electrode) The negative electrode 42 is a second electrode used to promote charge / discharge reactions, and as shown in FIG. 3, includes a negative electrode current collector 42A and a negative electrode active material layer 42B.

[0058] The negative electrode current collector 42A has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and the metal material is copper or the like.

[0059] The negative electrode active material layer 42B is provided on both sides of the negative electrode current collector 42A and contains one or more types of negative electrode active materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 42B may be provided on only one side of the negative electrode current collector 42A. The negative electrode active material layer 42B may further contain a negative electrode binder, a negative electrode conductor, and the like. Details regarding the negative electrode binder and the negative electrode conductor are the same as those regarding the positive electrode binder and the positive electrode conductor, respectively. The method for forming the negative electrode active material layer 42B is not particularly limited, but specifically includes one or more types of coating method, vapor phase method, liquid phase method, thermal spraying method, and firing method (sintering method).

[0060] The negative electrode active material contains one or both of a carbon material and a metal-based material. This is because a high energy density can be obtained. Carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). Metal-based materials are materials containing one or more metal elements and metalloid elements that can form an alloy with lithium as constituent elements, and the metal elements and metalloid elements are one or both of silicon and tin. However, the metal-based material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. Specific examples of metal-based materials are TiSi2 and SiOx (0 <x≦2、または0.2<x<1.4)などである。

[0061] Here, the height of the negative electrode 42 is greater than the height of the positive electrode 41. That is, the negative electrode 42 protrudes upward from the positive electrode 41 and also protrudes downward from the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from being deposited. This "height" is a dimension corresponding to the height H of the secondary battery described above, that is, the dimension in the vertical direction in each of FIGS. 1 and 2. The definition of height described here will also be applied hereinafter.

[0062] (separator) 2 and 3, the separator 43 is an insulating porous film disposed between the positive electrode 41 and the negative electrode 42. The separator 43 allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 contains a polymer compound such as polyethylene.

[0063] 2, the height of the separator 43 is greater than the height of the negative electrode 42. That is, the separator 43 preferably protrudes upward from the negative electrode 42 and also protrudes downward from the negative electrode 42.

[0064] (electrolyte) The electrolyte solution is impregnated into each of the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt. The solvent contains one or more of non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds, and the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more of light metal salts such as lithium salts.

[0065] [Positive lead] As shown in Fig. 2, the positive electrode lead 51 is housed inside the outer can 10. The positive electrode lead 51 is a connecting wire connected to each of the positive electrode 41 and the external terminal 20. The secondary battery shown in Fig. 2 has one positive electrode lead 51. However, the secondary battery may have two or more positive electrode leads 51.

[0066] The positive electrode lead 51 is connected to the upper end of the positive electrode 41. Specifically, the positive electrode lead 51 is connected to the upper end of the positive electrode current collector 41A. The positive electrode lead 51 is also connected to a part of the surface 20S of the external terminal 20 via a through hole 12K provided in the lid 12. The method for connecting the positive electrode lead 51 is not particularly limited, but specifically, it is any one or more of welding methods such as resistance welding and laser welding. The details of the welding methods described here also apply hereinafter.

[0067] A portion of the positive electrode lead 51 is electrically insulated from the lid portion 12 of the outer can 10 and the negative electrode 42 of the battery element 40, and is sandwiched between the lid portion 12 and the battery element 40 in the height direction of the secondary battery. As shown in FIG. 2 , the positive electrode lead 51 includes a first portion 511, a second portion 512, and a folded portion 513. The first portion 511 and the second portion 512 extend along a horizontal plane perpendicular to the height direction Z of the secondary battery. The first portion 511 and the second portion 512 overlap each other in the height direction Z of the secondary battery via a sealant 61. The folded portion 513 is curved to connect the first portion 511 and the second portion 512. The first portion 511 and the second portion 512 are sandwiched between the battery element 40 and a recessed portion 12H of the lid portion 12 in the height direction Z of the secondary battery.

[0068] FIG. 4A is a plan view illustrating an example of the configuration of the positive electrode lead 51. Specifically, FIG. 4A schematically illustrates the joint between the positive electrode lead 51 and the external terminal 20 as viewed from the battery element 40 inside the outer can 10. FIG. 4B is a cross-sectional view illustrating a cross section along the longitudinal direction of the positive electrode lead 51. Specifically, FIG. 4B illustrates a cross section of the positive electrode lead 51 along line IVB-IVB illustrated in FIG. 4A. FIG. 4C is a cross-sectional view illustrating a cross section of the positive electrode lead 51 along the width direction perpendicular to the longitudinal direction. Specifically, FIG. 4C illustrates a cross section of the positive electrode lead 51 along line IVC-IVC illustrated in FIG. 4A. Note that FIGS. 4A to 4C each illustrate an enlarged view of a portion of the positive electrode lead 51 welded to the back surface 20BS of the external terminal 20 and its vicinity. In addition, in FIGS. 4A to 4C, the longitudinal direction of the positive electrode lead 51 is defined as the L-axis direction, and the width direction of the positive electrode lead 51 is defined as the W-axis direction.

[0069] The positive electrode lead 51 has a first end 51A, a central portion 51C, and a second end 51B, arranged in this order along a width direction (W-axis direction) perpendicular to the longitudinal direction (L-axis direction). The central portion 51C is flat and extends along the back surface 20BS of the external terminal 20, and includes one or more welded portions WP welded to the back surface 20BS of the external terminal 20. FIGS. 4A and 4B illustrate two welded portions WP1 and WP2. In this secondary battery, as shown in FIG. 4C, the first end 51A and the second end 51B of the positive electrode lead 51 are bent in a direction away from the back surface 20BS of the external terminal 20. Note that while FIG. 4C illustrates an example in which both the first end 51A and the second end 51B are bent, it is sufficient in the present disclosure that at least one of the first end 51A and the second end 51B bent in a direction away from the back surface 20BS of the external terminal 20.

[0070] The positive electrode lead 51 may further have two recesses U1 and U2. The two recesses U1 and U2 are formed on the front surface 51FS of the central portion 51C opposite the back surface 20BS of the external terminal 20, and are aligned in the longitudinal direction (L-axis direction) of the positive electrode lead 51. The planar shape of the recesses U1 and U2 is, for example, a substantially semicircular shape or a substantially partial annular shape. Here, one or more welding points WP are located between the recess U1 and the recess U2.

[0071] If the outer diameter D of the exterior can 10 of the secondary battery is, for example, 16 mm, the dimension of the positive electrode lead 51 in the width direction is 4 mm or less.

[0072] In this way, the positive electrode lead 51 includes a flat central portion 51C and first and second end portions 51A and 51B located on either side of the central portion 51C and bent away from the back surface 20BS. This makes the shape of the positive electrode lead 51 less likely to be deformed by external forces. Therefore, for example, when welding the positive electrode lead 51 to the back surface 20BS, the flatness of the central portion 51C is less likely to be damaged. Therefore, the central portion 51C and the back surface 20BS are welded with high welding strength. As a result, the positive electrode lead 51 is less likely to fall off the back surface 20BS of the external terminal 20 even when the secondary battery is subjected to external forces such as vibration and impact.

[0073] Furthermore, a portion of the positive electrode lead 51 extends along the lower surface of the lid portion 12 and the upper surface of the battery element 40, and is thereby held by the lid portion 12 and the battery element 40. Therefore, the positive electrode lead 51 is fixed inside the outer can 10. Even if the secondary battery is subjected to external forces such as vibration and impact, the positive electrode lead 51 is less likely to move, and therefore the positive electrode lead 51 is less likely to be damaged. Damage to the positive electrode lead 51 here refers to the occurrence of cracks in the positive electrode lead 51, the positive electrode lead 51 being cut, the positive electrode lead 51 falling off from the positive electrode 41, etc.

[0074] That is, "a portion of the positive electrode lead 51 is sandwiched between the outer can 10 and the battery element 40" means that the positive electrode lead 51 is insulated from the outer can 10 and the battery element 40 while being held from above and below by the outer can 10 and the battery element 40, so that the positive electrode lead 51 is unlikely to move inside the outer can 10 even if the secondary battery is subjected to external forces such as vibration and impact. The fact that the positive electrode lead 51 is unlikely to move inside the outer can 10 means that the battery element 40 is also unlikely to move inside the outer can 10. Therefore, when the secondary battery is subjected to vibration or impact, problems such as collapse of the battery element 40, which is a wound electrode body, can be avoided.

[0075] Here, as described above, the lid portion 12 includes the recessed portion 12H, and a portion of the positive electrode lead 51 is sandwiched between the recessed portion 12H and the battery element 40. That is, a portion of the positive electrode lead 51 extends along the lower surface of the recessed portion 12H and the upper surface of the battery element 40, and is thereby held by the recessed portion 12H and the battery element 40. Since the positive electrode lead 51 is more easily held by utilizing the recessed portion 12H, the positive electrode lead 51 is less likely to be damaged.

[0076] Furthermore, a portion of the positive electrode lead 51 is insulated from the lid portion 12 and the negative electrode 42 via the separator 43, the sealant 61, and the insulating films 62 and 63, respectively.

[0077] Specifically, as described above, the height of the separator 43 is greater than the height of the negative electrode 42. As a result, a portion of the positive electrode lead 51 is separated from the negative electrode 42 via the separator 43, and is therefore insulated from the negative electrode 42 via the separator 43. This is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.

[0078] The positive electrode lead 51 is also coated with an insulating sealant 61. As a result, a portion of the positive electrode lead 51 is insulated from the lid portion 12 and the negative electrode 42 via the sealant 61. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented, and a short circuit between the positive electrode lead 51 and the negative electrode 42 is also prevented.

[0079] Furthermore, an insulating film 62 is disposed between the lid portion 12 and the positive electrode lead 51. As a result, a portion of the positive electrode lead 51 is insulated from the lid portion 12 via the insulating film 62. This is because a short circuit between the positive electrode lead 51 and the lid portion 12 is prevented.

[0080] Furthermore, an insulating film 63 is disposed between the battery element 40 and the positive electrode lead 51. As a result, a portion of the positive electrode lead 51 is insulated from the negative electrode 42 via the insulating film 63. This is because a short circuit between the positive electrode lead 51 and the negative electrode 42 is prevented.

[0081] The details regarding the material for forming the positive electrode lead 51 are the same as the details regarding the material for forming the positive electrode current collector 41A. However, the materials for forming the positive electrode lead 51 and the positive electrode current collector 41A may be the same as or different from each other.

[0082] Here, the positive electrode lead 51 is connected to the positive electrode 41 in a region in front of the center line PC, i.e., a region to the right of the center line PC in FIG. 2 . The positive electrode lead 51 has a folded portion 513 on its way to the external terminal 20 in order to be connected to the external terminal 20. The folded portion 513 is located in a region behind the center line PC, i.e., a region to the left of the center line PC in FIG. 2 . The positive electrode lead 51 has a first portion 511 as a portion extending from the point where it is connected to the positive electrode 41 through the center position P0 to the folded portion 513. The first portion 511 extends along the upper surface of the battery element 40 in a direction perpendicular to the height direction Z. Furthermore, the positive electrode lead 51 has a second portion 512 as a portion extending from the folded portion 513 to the point where it is connected to the external terminal 20. The second portion 512 extends along the upper surface of the battery element 40 in a direction perpendicular to the height direction Z so as to overlie the first portion 511. In this way, a portion of the positive electrode lead 51 extends toward the external terminal 20 while being sandwiched between the lid portion 12 and the battery element 40 in both the region in front of the center line PC and the region behind the center line PC.

[0083] Here, as is clear from FIG. 2, when the battery element 40 is divided into two regions based on the center line PC in the direction along the outer diameter D, the "region in front of the center line PC" refers to one of the regions where the connection point of the positive electrode lead 51 to the positive electrode 41 is present. In FIG. 2, the "region in front of the center line PC" refers to the region to the right of the center line PC. In contrast, as is clear from FIG. 2, the "region behind the center line PC" refers to the other of the two regions, which is the region to the left of the center line PC in FIG. 2. In other words, when the battery element 40 is divided into two regions based on the center line PC in the direction along the outer diameter D, the "region behind the center line PC" refers to the other region where the connection point of the positive electrode lead 51 to the positive electrode 41 is not present.

[0084] The connection position of the positive electrode lead 51 to the positive electrode 41 is not particularly limited and can be set arbitrarily. In particular, it is preferable that the positive electrode lead 51 be connected to the positive electrode 41 at a position closer to the inner periphery than the outermost periphery of the positive electrode 41. This is because, unlike when the positive electrode lead 51 is connected to the positive electrode 41 at the outermost periphery of the positive electrode 41, corrosion of the outer can 10 due to creeping up of the electrolyte is prevented. This "creeping up of the electrolyte" refers to the electrolyte in the battery element 40 creeping up the positive electrode lead 51 and reaching the inner wall surface of the outer can 10 when the positive electrode lead 51 is disposed close to the inner wall surface of the outer can 10. When the electrolyte comes into contact with the outer can 10 due to "creeping up of the electrolyte," a phenomenon occurs in which the outer can 10 dissolves or discolors.

[0085] Here, the positive electrode lead 51 is folded back one or more times between the positive electrode 41 and the external terminal 20, and is therefore folded back one or more times. The number of times the positive electrode lead 51 is folded back is not particularly limited as long as it is folded back one or more times. "The positive electrode lead 51 is folded back" here means that the extension direction of the positive electrode lead 51 changes midway so as to form an angle greater than 90°. The folded back portion of the positive electrode lead 51 may have a curved shape, like the folded back portion 513, without being bent. Although FIG. 2 illustrates the case where the positive electrode lead 51 includes one folded back portion 513, the positive electrode lead 51 may include multiple folded back portions 513.

[0086] The positive electrode lead 51 is folded back at a folding back portion 513 midway from the positive electrode 41 to the external terminal 20. Specifically, as shown in FIG. 2 , the first portion 511 extends, in a horizontal plane perpendicular to the height direction of the secondary battery, from a first position P1 other than the center position P0 of the outer casing 10 to a second position P2 on the opposite side of the first position P1 as viewed from the center position. The second portion 512 extends from the second position P2 toward the center position P0. In the positive electrode lead 51, the overlapping portion of the first portion 511 and the second portion 512 is a surplus portion. In other words, it can be said that the positive electrode lead 51 has a length margin in its longitudinal direction.

[0087] This provides room for changing the orientation of the lid portion 12 relative to the housing portion 11 when forming the outer can 10 using the housing portion 11 and the lid portion 12 in the manufacturing process of the secondary battery, as will be described later. Also, when the secondary battery is subjected to external forces such as vibration and impact, the external forces are alleviated by utilizing the length margin of the positive electrode lead 51, making the positive electrode lead 51 less likely to be damaged. Furthermore, by utilizing the length margin of the positive electrode lead 51, the connection position of the positive electrode lead 51 relative to the positive electrode 41 can be changed as desired without changing the length of the positive electrode lead 51.

[0088] In this case, the length of the positive electrode lead 51 (total length including a length margin) is not particularly limited and can be set arbitrarily. In particular, the length of the positive electrode lead 51 is preferably equal to or greater than half the outer diameter D of the outer can 10. This is because the length of the positive electrode lead 51 ensures a length margin for standing the lid part 12 upright relative to the storage part 11, making it easier to stand the lid part 12 upright relative to the storage part 11.

[0089] The connection range of the positive electrode lead 51 to the external terminal 20 is not particularly limited. In particular, the connection range of the positive electrode lead 51 to the external terminal 20 is preferably sufficiently wide so that the positive electrode lead 51 is unlikely to fall off the external terminal 20, and is also preferably sufficiently narrow so that a length margin of the positive electrode lead 51 is obtained. The reason why the connection range of the positive electrode lead 51 to the external terminal 20 is preferably sufficiently narrow is that the portion of the positive electrode lead 51 that is not connected to the external terminal 20 becomes the length margin, and therefore the length margin of the positive electrode lead 51 becomes sufficiently large. .

[0090] The positive electrode lead 51 is provided as a separate body from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, the positive electrode lead 51 may be integrated with the positive electrode current collector 41A.

[0091] [Negative lead] As shown in FIG. 2, the negative electrode lead 52 is housed inside the outer can 10. The negative electrode lead 52 is electrically connected to both the negative electrode 42 and the outer can 10 (storage section 11). Therefore, the storage section 11 (bottom M2) is electrically connected to the negative electrode 42 via the negative electrode lead 52. Here, the secondary battery includes one negative electrode lead 52. However, the secondary battery may include two or more negative electrode leads 52.

[0092] The negative electrode lead 52 is connected to the lower end of the negative electrode 42, more specifically, to the lower end of the negative electrode current collector 42A. The negative electrode lead 52 is also connected to the bottom surface of the storage section 11. The method for connecting the negative electrode lead 52 is not particularly limited, but specifically includes one or more welding methods such as resistance welding and laser welding.

[0093] The negative electrode lead 52 may have a configuration similar to that of the positive electrode lead 51 shown in FIGS. 4A to 4C. FIG. 5A is a plan view illustrating an example of the configuration of the negative electrode lead 52. Specifically, FIG. 5A schematically illustrates the joint between the negative electrode lead 52 and the bottom portion M2 as viewed from the battery element 40 inside the outer can 10. FIG. 5B is a cross-sectional view illustrating a cross section along the longitudinal direction of the negative electrode lead 52. Specifically, FIG. 5B illustrates a cross section of the negative electrode lead 52 along line VB-VB illustrated in FIG. 5A. FIG. 5C is a cross-sectional view illustrating a cross section of the negative electrode lead 52 along the width direction perpendicular to the longitudinal direction. Specifically, FIG. 5C illustrates a cross section of the negative electrode lead 52 along line VC-VC illustrated in FIG. 5A. Note that FIGS. 5A to 5C illustrate enlarged views of the vicinity of a welded portion of the negative electrode lead 52 welded to the inner surface M2S of the bottom portion M2. 5A to 5C, the longitudinal direction of the negative electrode lead 52 is defined as the L-axis direction, and the width direction of the negative electrode lead 52 is defined as the W-axis direction. As shown in FIGS. 5A and 5C, the negative electrode lead 52 has a first end portion 52A, a central portion 52C, and a second end portion 52B, which are arranged in this order along the width direction (W-axis direction) perpendicular to the longitudinal direction (L-axis direction). The central portion 52C is flat so as to extend along the inner surface M2S of the bottom portion M2 and includes one or more welded portions WP welded to the inner surface M2S. FIGS. 5A and 5B illustrate two welded portions WP1 and WP2. In this secondary battery, as shown in FIG. 5C, the first end portion 52A and the second end portion 52B of the negative electrode lead 52 are bent in a direction away from the inner surface M2S of the bottom portion M2. Note that Figure 5C illustrates an example in which both the first end 52A and the second end 52B are bent, but in the present disclosure, it is sufficient that at least one of the first end 52A and the second end 52B is bent in a direction away from the inner surface M2S of the bottom M2.

[0094] The negative electrode lead 52 may further have two recesses U1 and U2, similar to the positive electrode lead 51. When the outer diameter D of the outer can 10 of the secondary battery is, for example, 16 mm, the dimension of the negative electrode lead 52 in the width direction is 4 mm or less.

[0095] In this way, the negative electrode lead 52 has the same configuration as the positive electrode lead 51. Therefore, for example, when the negative electrode lead 52 is welded to the inner surface M2S, the flatness of the central portion 52C is unlikely to be impaired. Therefore, the central portion 52C and the inner surface M2S are welded with high welding strength. As a result, even when the secondary battery is subjected to external forces such as vibration and impact, the negative electrode lead 52 is unlikely to fall off from the inner surface M2S of the bottom portion M2.

[0096] The details regarding the material for forming the negative electrode lead 52 are the same as the details regarding the material for forming the negative electrode current collector 42A. However, the materials for forming the negative electrode lead 52 and the negative electrode current collector 42A may be the same as or different from each other.

[0097] The connection position of the negative electrode lead 52 to the negative electrode 42 is not particularly limited and can be set arbitrarily. Here, the negative electrode lead 52 is connected to the outermost peripheral portion of the negative electrode 42 that constitutes the wound electrode body.

[0098] The negative electrode lead 52 is provided as a separate body from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, the negative electrode lead 52 may be integrated with the negative electrode current collector 42A.

[0099] [Sealant] 2, the sealant 61 is a first insulating member that covers the periphery of the positive electrode lead 51, and is formed by attaching two pieces of insulating tape to the front and back surfaces of the positive electrode lead 51. Here, the sealant 61 covers the periphery of the middle portion of the positive electrode lead 51 in order to connect the positive electrode lead 51 to the positive electrode 41 and the external terminal 20, respectively. Note that the sealant 61 is not limited to having a tape-like structure, and may have, for example, a tubular structure.

[0100] The sealant 61 contains one or more insulating materials such as insulating polymer compounds, and the insulating material is polyimide or the like.

[0101] [Insulating film] 2, the insulating film 62 is an insulating member disposed between the lid portion 12 and the battery element 40 in the height direction Z. Here, the insulating film 62 has a ring-shaped planar shape having an opening 62K at a position corresponding to the through hole 12K in the height direction Z.

[0102] Here, the insulating film 62 may be adhered to the lid portion 12 via an adhesive layer.

[0103] Furthermore, the insulating film 62 may contain one or more insulating materials such as insulating polymer compounds, etc. The insulating material contained in the insulating film 62 is polyimide, etc.

[0104] 2, the insulating film 63 is an insulating member disposed between the battery element 40 and the positive electrode lead 51. Here, the insulating film 63 has a flat plate-like shape. The insulating film 63 is disposed so as to shield the winding center space 40K and to cover the battery element 40 around the winding center space 40K.

[0105] The details regarding the material for forming the insulating film 63 are the same as the details regarding the material for forming the insulating film 62. However, the materials for forming the insulating film 63 and the insulating film 62 may be the same as or different from each other.

[0106] [others] The secondary battery may further include one or more other components.

[0107] Specifically, the secondary battery is equipped with a safety valve mechanism. This safety valve mechanism is configured to cut off the electrical connection between the outer can 10 and the battery element 40 when the internal pressure of the outer can 10 reaches or exceeds a certain level. Causes of the internal pressure of the outer can 10 reaching or exceeding a certain level include the occurrence of a short circuit inside the secondary battery and the secondary battery being heated from the outside. There are no particular restrictions on the location where the safety valve mechanism is installed, but it is preferable that the safety valve mechanism be installed on either the bottom portion M1 or M2, and more preferably on the bottom portion M2 to which the external terminal 20 is not attached.

[0108] The secondary battery may also have an insulator other than the insulating films 62, 64 between the exterior can 10 and the battery element 40. This insulator includes one or more types of insulating film and insulating sheet, etc., and prevents short-circuiting between the exterior can 10 and the battery element 40. The installation range of the insulator is not particularly limited and can be set as desired.

[0109] The outer can 10 is provided with a split valve. This split valve splits when the internal pressure of the outer can 10 reaches or exceeds a certain level, thereby releasing the internal pressure. There are no particular limitations on the location where the split valve is to be installed, but, similar to the location where the safety valve mechanism is installed, either the bottom M1 or M2 is preferred, and the bottom M2 is particularly preferred.

[0110] <1-2. Operation> When the secondary battery is charged, lithium is released from the positive electrode 41 in the battery element 40 and is absorbed in the negative electrode 42 via the electrolyte. On the other hand, when the secondary battery is discharged, lithium is released from the negative electrode 42 in the battery element 40 and is absorbed in the positive electrode 41 via the electrolyte. During these charge and discharge cycles, lithium is absorbed and released in an ionic state.

[0111] <1-3. Manufacturing method> FIG. 5 shows a perspective view of an exterior can 10 used in the manufacturing process of a secondary battery, and corresponds to FIG.

[0112] FIG. 5 shows the state in which the cover 12 is separated from the storage section 11 before the cover 12 is welded to the storage section 11.

[0113] In the following description, reference will be made to FIG. 5 as well as to FIGS. 1 to 4, which have already been described.

[0114] 6, to form the outer can 10, a storage section 11 and a lid section 12 that are physically separated from each other are prepared. The storage section 11 is a roughly bowl-shaped member in which a bottom section M2 and a side wall section M3 are integrated with each other, and has an opening section 11K. The lid section 12 is a roughly plate-shaped member that corresponds to the bottom section M1, and an external terminal 20 is attached in advance to a recess section 12H provided in the lid section 12 via a gasket 30.

[0115] However, the storage section 11 may be formed by preparing the bottom section M2 and the side wall section M3 which are physically separated from each other, and welding the side wall section M3 to the bottom section M2.

[0116] [Preparation of positive electrode] First, a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and the like. Next, the prepared positive electrode mixture is poured into an organic solvent or the like to prepare a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to both sides of a positive electrode current collector 41A to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B is compression-molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated, or the compression molding may be repeated multiple times. In this manner, the positive electrode 41 is prepared.

[0117] [Preparation of negative electrode] The negative electrode 42 is fabricated using a procedure similar to that for fabricating the positive electrode 41. Specifically, a negative electrode mixture, which is a mixture of a negative electrode active material, a negative electrode binder, a negative electrode conductor, and the like, is poured into an organic solvent to prepare a paste-like negative electrode mixture slurry. The negative electrode mixture slurry is then applied to both surfaces of the negative electrode current collector 42A to form the negative electrode active material layers 42B. The thickness T2 of the negative electrode outer active material layer 42B2 covering the negative electrode current collector outer surface 42A2 is set to be thicker than the thickness T1 of the negative electrode inner active material layer 42B1 covering the negative electrode current collector inner surface 42A1. The negative electrode active material layer 42B is then compression-molded using a roll press or the like. This completes the fabrication of the negative electrode 42.

[0118] [Preparation of electrolyte] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolytic solution.

[0119] [Secondary battery assembly] First, using a welding method such as resistance welding, the positive electrode lead 51, which is covered with a sealant 61, is connected to the positive electrode 41 (positive electrode current collector 41A), and the negative electrode lead 52 is connected to the negative electrode 42 (negative electrode current collector 42A).

[0120] Next, the positive electrode 41 and the negative electrode 42 are stacked with a separator 43 interposed therebetween, and the stack including the positive electrode 41, the negative electrode 42, and the separator 43 is wound to produce a wound body 40Z, as shown in Fig. 6. The wound body 40Z has a configuration similar to that of the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with an electrolyte solution. Note that the positive electrode lead 51 and the negative electrode lead 52 are not shown in Fig. 6.

[0121] Next, the wound body 40Z, to which the positive electrode lead 51 and the negative electrode lead 52 are respectively connected, is accommodated inside the accommodation section 11 through the opening 11K. In this case, the negative electrode lead 52 is connected to the accommodation section 11 using a welding method such as resistance welding. Next, an insulating film 63 is placed on the wound body 40Z.

[0122] Next, after preparing the lid portion 12 to which the external terminal 20 is attached via the gasket 30 and on which the insulating film 62 is already provided, the positive electrode lead 51 is connected to the external terminal 20 via the through hole 12K using a welding method such as resistance welding.

[0123] As a result, the wound body 40Z (positive electrode 41) housed inside the housing portion 11 and the external terminal 20 attached to the lid portion 12 are connected to each other via the positive electrode lead 51.

[0124] Next, the electrolyte solution is poured into the storage section 11 through the opening 11K. In this case, even if the battery element 40 and the external terminal 20 are connected to each other via the positive electrode lead 51 as described above, the lid section 12 does not close the opening 11K, so the electrolyte solution can be easily poured into the storage section 11 through the opening 11K. As a result, the wound body 40Z including the positive electrode 41, the negative electrode 42, and the separator 43 is impregnated with the electrolyte solution, and the battery element 40, which is a wound electrode body, is produced.

[0125] Next, the lid 12 is tilted down so as to approach the storage section 11, thereby closing the opening 11K with the lid 12, and then the lid 12 is welded to the storage section 11 using a welding method such as laser welding. In this case, as shown in Fig. 2, a part of the positive electrode lead 51 is sandwiched between the lid 12 and the battery element 40, and a curved folded-back portion 513 is formed in the positive electrode lead 51 before the connection point to the external terminal 20. In this way, the outer can 10 is formed, and the battery element 40 and the like are housed inside the outer can 10, completing the assembly of the secondary battery.

[0126] [Stabilization of secondary batteries] The assembled secondary battery is charged and discharged. Various conditions, such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions, can be set as desired. This forms a coating on the surface of the negative electrode 42, etc., which electrochemically stabilizes the state of the secondary battery. This completes the secondary battery.

[0127] <1-4. Actions and Effects> As described above, in the secondary battery of this embodiment, the positive electrode lead 51 includes a flat central portion 51C and first and second end portions 51A and 51B located on either side of the central portion 51C and bent away from the back surface 20BS. This increases the welding strength between the flat central portion 51C and the back surface 20BS of the external terminal 20. Therefore, even when an external mechanical load such as vibration or impact is applied to the battery, the positive electrode lead 51 does not come off the back surface 20BS of the external terminal 20, and a good electrical connection between the positive electrode lead 51 (positive electrode 41) and the external terminal 20 can be maintained. Furthermore, the positive electrode lead 51 has two recesses U1 and U2 aligned in its longitudinal direction, which improves the shape stability of the positive electrode lead 51. In other words, the provision of the two recesses U1 and U2 more stably maintains the shape of the positive electrode lead 51, which includes the flat central portion 51C and the first and second end portions 51A and 51B located on either side of the central portion 51C. When the negative electrode lead 52 has two recesses U1 and U2 aligned in the longitudinal direction thereof, the shape stability of the negative electrode lead 52 can be improved.

[0128] The recesses U1 and U2 are formed, for example, by pressing a jig having a substantially semicircular or substantially partially annular contact surface against the surface of the positive electrode lead 51. Here, the planar shape of the recesses U1 and U2 is substantially semicircular or substantially partially annular, so that cracks can be prevented from occurring in the positive electrode lead 51 when the recesses U1 and U2 are formed. For example, when two recesses each having a rectangular planar shape are formed by pressing a jig having a rectangular contact surface, cracks are likely to occur in the positive electrode lead 51. Therefore, by making the recesses U1 and U2 have a substantially semicircular or substantially partially annular planar shape, the reliability of the secondary battery of this embodiment is improved.

[0129] Furthermore, when the two recesses have a substantially circular planar shape, the need to provide a welding point WP between the two recesses tends to make the distance between the two recesses wider than when the recesses U1, U2 have a substantially semicircular or partially annular planar shape. Therefore, by having the recesses U1, U2 have a substantially semicircular or partially annular planar shape, it is easier to accommodate miniaturization of the secondary battery.

[0130] In the secondary battery of this embodiment, the negative electrode lead 52 further includes a flat central portion 52C and first and second end portions 52A and 52B located on either side of the central portion 52C and bent away from the inner surface M2S. This increases the welding strength between the flat central portion 52C and the inner surface M2S of the bottom portion M2. Therefore, even when an external mechanical load such as vibration or impact is applied to the secondary battery of this embodiment, the negative electrode lead 52 does not come off the inner surface M2S of the bottom portion M2, and good electrical connection between the negative electrode lead 52 (negative electrode 42) and the outer can 10 can be maintained. This ensures high reliability of the secondary battery of this embodiment.

[0131] Furthermore, in the secondary battery of this embodiment, a recessed portion 12H is provided in the lid portion 12, and the external terminals 20 are arranged in the recessed portion 12H. This allows the height dimension of the secondary battery to be reduced while ensuring the battery capacity.

[0132] In addition, the secondary battery is flat and columnar, i.e., the secondary battery is a coin type or button type. In the case of secondary batteries called such, positive electrode lead 51 is less likely to be damaged even in small secondary batteries that are subject to significant size restrictions, and therefore a greater effect can be obtained in terms of physical durability.

[0133] Furthermore, if the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the absorption and desorption of lithium.

[0134] Although the present technology has been described above with reference to one embodiment, the configuration of the present technology is not limited to the configuration described in the above embodiment and can be modified in various ways.

[0135] Specifically, the case where the outer can is a welded can (crimpless can) has been described, but the configuration of the outer can is not particularly limited, and it may be a crimped can that has been crimped. In this crimped can, the storage section and lid section, which are separated from each other, are crimped together via a gasket.

[0136] Furthermore, although the electrode reactant is described as lithium, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0137] Furthermore, in the above-described embodiment of the secondary battery, both the positive electrode lead 51 and the negative electrode lead 52 are described as having their widthwise ends bent, but in the present disclosure, it is sufficient that at least one of the positive electrode lead and the negative electrode lead has such a configuration.

[0138] In the secondary battery of the above embodiment, the positive electrode lead 51 is connected to the external terminal 20 and the negative electrode lead 52 is connected to the storage portion 11 of the outer can 10, but the present disclosure is not limited to this. That is, in the secondary battery of the present disclosure, the negative electrode lead may be connected to the external terminal and the positive electrode lead may be connected to an outer casing member.

[0139] Furthermore, in the above embodiment, a secondary battery is used as an example for explanation, but the battery of the present disclosure is not limited to a secondary battery, and can also be applied to a primary battery.

[0140] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0141] Furthermore, the present disclosure may take the following aspects. <1> a battery element including a first electrode and a second electrode; an exterior member that houses the battery element; an external terminal attached to the exterior member via an insulating member; a first electrode lead connecting the first electrode and the inner surface of the external terminal; a second electrode lead connecting the second electrode and the inner surface of the exterior member; Equipped with At least one of the first electrode lead and the second electrode lead has a first end, a central portion, and a second end in that order along a width direction perpendicular to a longitudinal direction of the lead; the central portion is flat and is welded to an inner surface of the external terminal or an inner surface of the exterior member; At least one of the first end and the second end is bent in a direction away from the inner surface of the external terminal or the inner surface of the exterior member. battery. <2> Both the first end and the second end of at least one of the first electrode lead and the second electrode lead are bent in a direction away from the inner surface of the external terminal or the inner surface of the exterior member. the above <1> Battery as described. <3> At least one of the first electrode lead and the second electrode lead is two recesses arranged in the longitudinal direction and formed on an inner surface of the external terminal or on a surface of the exterior member opposite to the inner surface; The outer terminal has one or more welded portions between the two recesses and the inner surface of the outer casing. the above <1> or <2> The battery described in <4> The exterior member has a generally cylindrical outer shape with a diameter of 16 mm, The width of the first electrode lead and the width of the second electrode lead are both 4 mm or less. the above <1> from <3> 1. A battery according to any one of the preceding claims. <5> The first electrode is a positive electrode and the second electrode is a negative electrode. the above <1> from <4> 1. A battery according to any one of the preceding claims. <6> the exterior member has a container including an insertion opening through which the battery element can be inserted in a first direction and capable of accommodating the battery element through the insertion opening, and a lid portion that closes the insertion opening and is provided with a through-opening that penetrates in the first direction, The external terminal is attached to the lid portion via the insulating member and overlaps the through hole. the above <1> from <5> 1. A battery according to any one of the preceding claims. <7> The outer edge of the lid is connected to the insertion port of the container by welding. the above <6> Battery as described. <8> the lid portion of the exterior member has a recessed portion recessed toward the battery element along the first direction, The through hole is provided in the recess. the above <6> or <7> Battery as described.

Claims

1. a battery element including a first electrode and a second electrode; an exterior member that houses the battery element; an external terminal attached to the exterior member via an insulating member; a first electrode lead connecting the first electrode and an inner surface of the external terminal; a second electrode lead connecting the second electrode and the inner surface of the exterior member; Equipped with At least one of the first electrode lead and the second electrode lead has a first end portion, a central portion, and a second end portion in this order along a width direction perpendicular to a longitudinal direction of the lead; the central portion is flat and is welded to an inner surface of the external terminal or an inner surface of the exterior member; At least one of the first end portion and the second end portion is bent in a direction away from an inner surface of the external terminal or an inner surface of the exterior member, At least one of the first electrode lead and the second electrode lead is two recesses arranged in the longitudinal direction and formed on an inner surface of the external terminal or on a surface of the exterior member opposite to the inner surface; The outer terminal has one or more welded portions between the two recesses and the inner surface of the outer casing. battery.

2. Both the first end and the second end of at least one of the first electrode lead and the second electrode lead are bent in a direction away from the inner surface of the external terminal or the inner surface of the exterior member. The battery of claim 1.

3. The exterior member has a generally cylindrical outer shape with a diameter of 16 mm, The width of the first electrode lead and the width of the second electrode lead are both 4 mm or less. The battery according to claim 1 or claim 2.

4. The first electrode is a positive electrode and the second electrode is a negative electrode. The battery according to claim 1 or claim 2.

5. the exterior member includes a container including an insertion opening through which the battery element can be inserted in a first direction and capable of accommodating the battery element through the insertion opening, and a lid portion that closes the insertion opening and is provided with a through-opening that penetrates in the first direction, The external terminal is attached to the lid portion via the insulating member and overlaps the through hole. The battery according to claim 1 or claim 2.

6. The outer edge of the lid is connected to the insertion port of the container by welding. The battery of claim 5.

7. the lid portion of the exterior member has a recessed portion recessed toward the battery element along the first direction, The through hole is provided in the recess. The battery of claim 5.

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